real-time graphics editing

Non-linear video editing with computers (NLE for short) has given us enormous freedom. Not only the fiddling with adhesive presses and cotton gloves, synchronised tape machines or even toxic carbon tetrachloride in magnetic magnifiers from the early days of videotape are a thing of the past. today, "cuts" are non-destructive and can be altered at will (sometimes all too often). But the whole thing has one disadvantage .....